Chart drive mechanism



NOV. 18, 1952 J CALDWELL 2,618,528

CHART DRIVE MECHANISM Original Filed June 20, 1942 3 Sheets-Sheet l 2 g5 3 L z INVENTOR. JOHN A: CALDWELL ATTORNEY FIG. I

NOV. 18, 1952 J, D L 2,618,528

CHART DRIVE MECHANISM Original Filed June 20, 1942 5 Sheets-Sheet 2 FIG.2

r INVENTOR. JOHN A. CALDWELL ATTORNEY.

NOV. 18, 1952 J D ELL 2,618,528

CHART DRIVE MECHANISM Original Filed Jl me 20, 1942 3 Sheets-Sheet 3INVENTOR. JOHN A. CALDWELL ATTORNEY Patented Nov. 18, 1952 CHART DRIVEMECHANISM John A. Caldwell, Philadelphia, Pa., assignor, by

mesne assignments, to

Regulator Company, M poration of Delaware Minneapolis-Honeywellinneapolis, Minn, a cor- Original application June 20, 1942, Serial No.

447,863. Divided and this application October 24, 1946, Serial No.705,303

6 Ciaims.

The present invention is a division of my copending application, SerialNumber 447,863, filed on June 20, 1942, now Patent No. 2,423,480,patented July 8, 1947. That application is directed generally to amultiple self-balancing potentiometer of the strip chart type, while thepresent application is specifically related to the chart supply andreroll mechanism that is used in the potentiometer.

In recording potentiometers there is provided a recording mechanism thatis moved through a path to various positions corresponding to the valueof the condition under measurement. This recording mechanism may eitherinclude a pen that is dragged across a chart or, as in the present case,include a print wheel that is adapted to print sequentially .the valueof a plurality of variables. In either event there is supplied a chartthat is moved at a constant rate of speed past the recordin station.This chart is generally supplied in a roll that is mounted in themachine. During the time that the instrument is in operation chart isdrawn from the supply roll, passed through a recording location andrerolled upon a take-up roll.

In the operation of the chart drive mechcanism it is highly desirablethat a simple and reliable means be provided to hold the supply andtakeup rolls. Such a means must be readily adjusted to shift the rollsand the chart extending between them axially so that the chart will becorrectly positioned with respect to the path of travel of the recordingelement. It is also desirable to be able to insert and remove the chartrolls with a minimum of time and trouble.

It is therefore an object of the invention to provide a recordinginstrument in which the chart is easily accessible for inspection andmay be readily and quickly changed when a new chart is needed. The chartsupply and rewind mechanism is also supplied with novel adjusting meansto compensate for irregularly wound rolls of chart paper.

It is a further object of the invention to supply novel and improvedchucks for supportin and driving the supply and take-up rolls of thechart.

It is also an object of the invention to provide an improved chartbacking plate which may easily be moved from its operative position toone in which the supply roll, which normally lies behind it, may beeasily replaced.

The various features of novelty which characterize this invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding or the invention,however, its advantages and specific objects obtained with its use,reference should be had to the accompanying drawings and descriptivematter in which is illustrated and described a preferred embodiment ofthe invention.

In the drawings:

Figure l is a front view of the instrument in its casing with certainportions broken away,

Figure 2 is aback view of the supporting frame for the recordinginstrument with certain portions broken away,

Figure 3 is a sectional view showing a chuck for supporting one end ofboth the chart supply roll and the chart take-up roll,

Figure 4 is a sectional view showing a supporting chuck for the otherend of the chart supply roll, and

Figure 5 is an outside view of the left hand sideplate of the frame ofthe instrument with associated parts mounted thereon.

The details of construction of the entire potentiomete instrument areshown and described in the above mentioned parent application. Thedescription in this application will be restricted to those parts whichare necessary for a complete disclosure of the invention claimed herein.Reference is made to the parent application for further details ofapparatus which is shown but not described in this case.

As is known, self-balancing potentiomete instruments are provided withan electrical network that is normally balanced. When, however, thetemperature under measurement changes, the E. M. F. produced by athermocouple, which in this case is the responsive element, varies sothat the potentiometer circuit is unbalanced, this acts through suitableelectrical apparatus forming a part of the instrument to energize areversible motor 5 for rotation in one direction or an oppositedirection until the instrument is again balanced. Rotation of the motor5 is imparted to a recording mechanism to move this recording mechanismto a position that is proportional to the value of the temperature orother condition which is under measurement.

The entire potentiometer mechanism is housed within a casing that isprovided with a door Bl which is hinged on one side at 68 and which maybe opened to give access to the interior thereof. This door is providedwith a suitable window 70 through which the recording mechanism and aportion of the chart that has a record upon it may be seen. Mounted inthe casing is a chassis or frame 12 upon which various of the parts,including the recording mechanism, are mounted. This chassis is hingedin the casing at H and may be swung out of the casing in order to giveaccess to the parts on the rear thereof which are shown on Figure 2. Itwill be seen that the instrument is provided with a chart 2 I 9 uponwhich a record is made by a print wheel 92. Moving with the print wheelis a pointe I34 that coo-perates with a scale I35 which extends acrossthe instrument. Thus, at any time an attendant may have an indication ona large legible scale of the value of the temperature and simultaneouslywill receive a record of the value of the temperatures which may besaved for future use.

Motor which is shown in dotted outline in Figure 2 is energized forrotation in one direction or another in response to potentiometerunbalance. This motor has on its shaft a. pinion 258 which meshes withgear 58 to rotate the latter as the motor rotates. Fastened to the gearis a pulley 59 around which a cable 80 passes. As the pulley is rotated,the cable which extends across the back of the instrument around pulleysI45, I46, I41, I48, continues in a loop across the front of theinstrument where it is attached to a carriage upon which print wheel 92is mounted. Therefore as the motor is energized the print wheel will bemoved back and forth across the chart to positions proportional to thetemperature under measurement. From time to time when the motor hasstopped rotating thus indicating that the instrument is in balance theprint wheel is moved into recording engagement with the chart in orderto make a record of the temperature. Immediately thereafter theinstrument is connected to another thermocouple so that the record ofanother temperature may be made on the same chart. Mechanism is providedto detect balance of the potentiometer network and operate the printingmechanism. The details of this construction are not pertinent to thepresent disclosure. It may be stated however that upon balance of thepotentiometer network a crank I19 shown in Figure 5 is rotated through acomplete revolution. As this crank is rotated a roller I12 on its endmoves in a cam slot I13 formed in a lever Ht that is pivoted formovement arounda shaft I15. Crank I1IJ moves in a clockwise directionand as it moves past point I80 in the cam slot lever I14 will be movedin a clockwise direction. This lever is mechanically connected with theprint Wheel so that as it moves print wheel 92 is moved downwardly inFigure 5 into engagement with the chart. Continued rotation of crank Iwill move lever I16 in a counterclockwise direction and then in aclockwise direction to the position shown where it will be ready to makeanother recording when the instrument again reaches a balancedcondition. Movement of the lever I14 in addition to actuating the printwheel for recording purposes also causes the print wheel to rotate inorder to bring another printing character thereon into position andsimultaneously operates a selector switch 195 shown in Figure 2 toconnect another thermocouple to the potentiometer network.

In order that a continuous record may be made, it is necessary that somemeans be provided to move the chart through the instrument at a constantrate and that some means be provided to adjust the chart with respect tothe travel of the print wheel so that the record will be placed properlyon the chart. The present invention is directed specifically to themeans for supporting and driving the recording chart. The chart 2 I9which has been mentioned above, is shown best in Figure 1. It will beseen that the chart is provided with horizontal and vertical lines, andhas on one edge a series of round holes 220, and on its opposite edge aseries of slots 22I. The horizontal lines on the chart serve the purposeof indicating the time at which some particular record is made, whilethe vertical lines or calibration marks serve to indicate the value ofthe temperature that has been recorded. As best seen in Figure 5, supplyroll 222 of the chart is mounted between the ends of the frame 12 nearthe bottom, and toward the rear of the frame. The chart, when beinginserted into the instrument is pulled upwardly, and forwardly over therod 223. The chart is then threaded toward the rear of the instrumentbetween a guide member 224, and the chart drum I44. This guide member'serves to direct the chart around the drum, from which it is broughtdown across the front of the instrument, and over a chart backing plate225 to a chart take up roll 22%, which is located at the bottom of theframe directly in front of the supply roll.

The backing plate its lower end, as shown at moved out of the way when anew chart is to be inserted into the instrument. Ihe backing plate isheld in place by means of a pair of lock members 228 that engage cut-outportions 229 on the upper corners of the backing plate.

These locking members are held in engagement with the portions 229 ofthe backing plate by means of spring members 239 upon which they aremounted.

The supply roll 222 and the take-up roll 226 are mounted at their leftends in Figure 1, or their right ends in Figure 2, in the frame portion12A upon a spring mounted chuck 23I shown in Figure 3 which is adaptedto be wedged into the end of the core 232 of a supply or take-up roll.This chuck is attached to a shaft 233 that is mounted for rotation in abushing 234 inserted in the frame 12A. The chuck is forced to the leftin Figure 3 into engagement with the end of the roll by means of aspring 235, and is limited in its movement by a washer 236 on the outerend of the shaft. It will be noted that the shaft 233 is made of a largediameter near the chuck and a small diameter to the right thereof. Thisconstruction gives a large and rigid bearing surface near the end of thechart roll and permits the use of a bushing 234 of the type shown whichfully encloses the spring 235.

The left end of the supply roll 222 in Figure 2 or the end in frameportion 123 is mounted on a non-rotatable chuck 292 shown in Figure 4,that is attached to a shaft 293 which is threaded through the frame 12B.This shaft may be provided with a knob 294 to rotate it and shift thechuck axially. In any event a lock nut 295 is threaded over the shaftand is jammed against the frame to hold the chuck firmly in positionwhen it has been adjusted. Sinc the chuck 2192 is non-rotatable itserves to put a drag on the supply roll to prevent the same fromoverrunning. Both the chuck which supports the left endof the supplyroll and that which supports the left end of the take-up roll, to bedescribed below, are axially adjustable so that the rolls may be shiftedto the proper position relative to the chart drum I 44. Theright end ofthe take-up roll 226 adjacent frame portion 123 is supported by anadjustable and rotatable chuck 231 shown in detail in Figure 2. Thecheek" is provided witha tongue238 that is adapted to engage the usualdriving notch formed in the 225 is preferably hinged at 221, so that itmay be end of the roll core (see Figure 1). This tongue extends throughan opening in the edge of the chuck and is formed of spring materialwhich always acts to move out into the position shown. When inserting aroll over a chuck of this type, the tongue 238 will be moved against theflange of the chuck. Thereafter, as the roll or the chuck is rotated,the tongue will spring into its driving position as soon as the drivingnotch of the core is in alignment therewith. The chuck 231 is attachedto a shaft 239 whose outer end is provided with a knob 240 whereby thechuck can be rotated at will to supply or tak up slack in the chart. Theshaft 239 is journaled in a sleeve 24! that is threaded through anopening in the frame 12. The outer end of this sleeve is provided with athumb nut 242 whereby the sleeve can be rotated in order to shift thechuck to its proper axial position and is provided with a lock nut 243that can be jammed against the side of the frame to hold the bearing inplace.

The chuck used for the take-up roll has attached to the shaft 239 asprocket 244. This sprocket is driven by a chain 245 that extends over asecond and larger sprocket 246. An idler sprocket may be used againstthe chain to take up slack if this is deemed necessary. In order tocompensate for increasing diameter of the chart on the take-up drum thesprocket 246 is frictionally driven by the chart drum M4 by means of apair of friction washers 247 that are keyed to a shaft 248 on the end ofthe chart drum. The sprocket and the friction washers are moved togetherand against a nut 249 that is screwed on the shaft by means of a plate253 which is forced to the left by springs 252. Each of the springs 252surround a plunger 25! which is attached to the plate 259 and which isfreely movable through openings that are formed in the end of the chartdrum. In order to adjust the tension of the springs, and therefore thefriction with which the sprocket 246 is driven, the nut 249 may be movedto the left or right along the shaft 248.

The chart drum in this embodiment of the invention is driven at aconstant speed by the motor 64 through a gear train 253 that starts withthe pinion 64A (Figures 2 and 5) and ends with the gear 254 that isfrictionally mounted on the drum. It will be seen from Figure 1 that thechart drum is provided on each end with a series of projections 255 thatproject through the openings 22!! and 22! on the chart. By means ofthese projections and openings the chart is positively moved past theprint wheel at some given speed. The speed of the chart drum may ofcourse be changed by substituting a different gear reduction between themotor and the chart drum. The shaft upon which the chart drum is mountedis provided with a knob 256 by means of which the chart drum may berotated to position properly the chart with respect to the print wheel.There is also provided a member 296 which extends over the edge of thechart and which can be used as a guide to set properly the time lines onthe chart relative to the print wheel and a so-called tear-off strip25'! which is made of some transparent material and which extends acrossthe instrument in front of the chart. The purpose of this member is toact as a straight edge when a piece of the chart is to be removed.

From time to time it becomes necessary to replace the chart roll in theinstrument. When this is done the empty core 232 which will be on thesupply roll chucks is removed from those chucks and placed on thetake-up roll chucks 23] and 23'! which are shown in the lower right handcorner of Figure 5. Locking members 223 are then moved upwardly out ofnotches 22%! on the chart backing plate 225. This plate may then bemoved forwardly around its pivots 22'! until it is completely out of theway. The new chart roll is then placed on the chucks 23! and 292. Theleading end of the chart is then removed from the chuck and pulledforwardly around rod 223, threaded between guide 224 and chart drum l .4and enough of this chart is pulled off of the supply roll to extend downthe front of the instrument and be wrapped around the take-up roll core.The chart backing plate is then moved back into position and the end ofth chart is brought down in front of this plate and suitably attached tothe core of the take-up roll. Thereafter the chart drive mechanism,which is run by motor 34, will forward the chart and rewind it in amanner above described.

When charts of this type are printed great pains are taken to make surethat the calibration marks always come the same distance from the rightedge of the chart in Figure 1 so that when the perforations on the chartare placed over the projections 255, the chart will be properly alignedin the instrument. It is therefore necessary that the chucks for theright hand end in Figure 1 of the supply and take-up rolls be adjustedaxially so that the chart will be pulled straight through the machine.If the chucks are not properly adjusted there will be a tendency to tearthe chart. Normally speaking the chucks will only have to be adjustedwhen the first roll is put into the instrument because of the care withwhich the chart is printed and wound. It may be, however, that a roll ofchart has been dropped and slightly telescoped. In such a case minoradjustment of the supporting chucks will be necessary. Since the chuckswhich support the left hand end of the rolls in Figure 1 are springpressed toward the right, these chucks will automatically assume theproper positions.

From the above description it will be seen that I have provided a simpleand reliable means for mounting and driving a chart in a recordinginstrument. By means of the construction shown the chart is driven at aconstant rate of speed through the instrument and in a path which can beadjusted for different charts but which always insures that the chartwill be properly lined up with respect to the travel of the recordingelement.

While in accordance with the provisions of the statutes, I haveillustrated and described the best forms of the invention now known tome. it will be apparent to those skilled in the art that changes may bemade in the form of the apparatus disclosed without departing from thespirit of the invention as set forth in the appended claims, and that insome cases certain features.

of the invention may sometimes be used to ad-- vantage without acorresponding use of otherfeatures.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a measuring and recording instrument, a frame including a pair ofparallel sides, a chart drum mounted for rotation in said sides. supplyand take-up holding means for a roll of chart paper mounted in saidsides below and 7 slightly behind said chart drum, a chart backing platemounted between said sides below said chart drum and in front of saidholding means, means to pivot said backing plate to said sidesindependent of said holding means whereby said backing plate can beswung forwardly to give access to said holding means, and means toreleasably maintain said backing plate in position below said chartdrum.

2. In a recording instrument, a frame having a pair of parallel sides, achart drum mounted for rotation in said sides, supply and take-upholding means for a roll of chart paper mounted below and slightly tothe rear of said chart drum, the chart passing upwardly and forwardlyover said chart drum and downwardly to said takeup holding means, guidemeans to direct the chart around said chart roll, chart backing meanslocated below said chart drum and in front of said mounting means overwhich the chart passes on its way from the chart drum to the take-upholding means, means to pivotally mount said backing means at its lowerend on said sides independent of said holding means whereby the backingmeans may be swung forwardly to give access to said mounting means, andresilient holding means to maintain said backing means in place.

3. In a recording instrument, the combination of a rectangular casinghaving an open front, a door to close said front hinged to one side ofsaid casing, a frame member hinged tothe opposite side of said casingnear the front, recording means carried by said frame, a rotatable chartdrum mounted below said recording means and adapted to support a chartin a position to be recorded upon by said recording means, means locatedon said frame below and to the, rear of said chart drum to support asupply roll of paper comprising a spring pressed plunger adapted toengage one end of said roll and a chuck to en: gage the other end ofsaid roll, means to mount said chuck for axial movement and means tolock said chuck against rotation and axial movement, means to guidepaper from the supply roll to said chart drum, means to take-up paper ona roll from said chart drum locatedon said frame below said chart drumand adjacent the supply roll comprising a second chuck having a surfaceupon which one end of is to be mounted by engagement therewith and aflange adapted to engage the end of the roll, a driving member extendingthrough said surface and resiliently moved to a position remote fromsaid flange, supporting means to rotatably said second chuck, means toshift said supporting means axially, means to lock said supporting meansin position, means to rotate said-second chuck, a chart backing platelocated below said chart drum and above and in frontof said take-up rollsupport, means to pivot said backing means to said frame whereby it maybe moved to give access to the supply and take-up rolls, and means tolock resiliently said backing plate in operative position.

4. In an instrument for making a'record on a strip chart, a support,supporting means on which the. take-up roll a mount a roll of said stripchart is mounted on said sup port, a part to back up said strip chartafter a record has been made thereon, pivots mounting said part at itslower end to said support for turning movement about an axis transverseto the path of movement of said strip chart and separate from thesupporting means for mounting said strip chart on said support so thatsaid supporting means are not disturbed, and means to hold said part innormal position beneath said strip chart.

5. In an instrument for making a record on a strip chart, recordingmeans movable through a path, a chart drum extending along said pathadjacent said recording means, supply and takeup means located belowsaid drum and adapted to mount a roll of the strip chart thereon, asupport on which said recording means and said drum and said supply andtake-up means are mounted, a part to back up said strip chart after arecord has been made thereon and located below said drum approximatelytangent thereto, said part extending the length of said drum, means topivot said part at its lower end to said support for turning movementabout an axis 7 parallel to said path, while said supply and takeupmeans remain stationary, and means to hold said part in position beneathsaid drum.

6. In an instrument for making a record on a strip chart, a frame havingforwardly projecting sides, means for supporting a roll of the stripchart on said sides, a backing plate adapted to underlie said chart whenthe chart is in operative position, said backing plate being hinged tosaid sides for movement about its hinges independently of said means forsupporting said roll of the strip chart so as to afiord access to saidmeans which means remain stationary in their normal position; saidbacking plate having cut-out portions, lock members having substantiallyconical front faces and substantially flat rear faces, and springmembers mounting said lock members so that said lock members are movedaside slightly by the edges of said cut-out portions as said backingplate is turned toward its normal portion underlying said chart, andsaid lock members then latch over the edges of said cut-out portions sothat the flat rear faces of the lock members engage and hold the edgesof said backing plate while said backing plate is in its normalposition.

' JOHN A. CALDWELL.

REFERENCES CITED lhe following references are of record in the file ofthis patent:

UNITED STATES PATENTS

